Communication networks of various kinds are known. A communication session typically comprises the facilitation of communications between two or more user platforms. In more recent times increased interest exists with respect to using Session Initiation Protocol (SIP)-based platforms to support and facilitate one or more aspects of such communication sessions. Using such an approach a Session Initiation Protocol server can be employed to support various communication session activities. For example, on-hold status for one or more user platforms can be supported in this manner.
Mobile user platforms are also known in the art. Such user platforms may comprise, for example, a personal device that a given user carries on their person. Such mobile user platforms may exhibit mobility before, during, and/or after a given communication session. An increasing number of such mobile platforms comprise multi-network user platforms and are capable of compatible operation on more than one type of communication network. Mobility in the case of a multi-network user platform, of course, can lead to a need to hand off a given user platform from one network to another in order to ensure the provision of adequate communication connectivity.
At present, when a first communication network hands off a given user platform to a second communication network during the course of a communication session where that communication session is serviced by (and terminable by) a Session Initiation Protocol server as comprises a part of that first communication network, the Session Initiation Protocol server will terminate the communication session.
This occurs at least in part because all Session Initiation Protocol dialogs typically terminate when a corresponding active user platform leaves the network as occurs during such a hand off. This means, in part, that the Session Initiation Protocol server no longer receives status and/or control messages and/or responses (such as, for example, caller identification information, Session Initiation Protocol INVITE messages, and so forth) that it expects to receive from the handed-off user platform. At some point the Session Initiation Protocol server simply concludes that the corresponding mobile station has been lost and accordingly terminates the session.
This, of course, can present problems. Most end users will object to having their ongoing communications abruptly interrupted in this manner. Furthermore, in many or most cases, the user receives no specific indication that a hand off has occurred. The user is therefore not only frustrated with respect to their intentions but have no information by which to ascertain the nature or cause of the failure. It would be possible, of course, to reprogram (or replace) Session Initiation Protocol servers to behave differently than has been described above. Existing legacy Session Initiation Protocol server installations, however, are numerous, represent a significant investment, and are not under common administrative control. All of these factors make such a solution paradigm undesirable and unlikely to be implemented in the near future.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.